The present invention relates to a method of manufacturing components for a tire for vehicle wheels, of the type comprising the steps of: a) feeding an elongated element from a delivery member disposed adjacent to an outer surface of a toroidal support; b) giving the toroidal support a rotatory motion for circumferential distribution around a geometric axis of rotation thereof, so that the elongated element is circumferentially distributed onto the toroidal support; c) carrying out controlled relative displacements between the toroidal support and the extrusion die so as to form with said elongated element, a plurality of coils disposed mutually in side by side relationship in order to define a tire component.
The invention also relates to an apparatus for manufacturing components for a tire being worked, of the type comprising: a toroidal support arranged for carrying the components of a tire being worked; feeding devices or other convenient feeder means for feeding at least one elongated element through a delivery member disposed adjacent to an outer surface of the toroidal support; circumferential-distribution devices or other convenient circumferential-distribution means arranged to drive the toroidal support in rotation around a geometric axis thereof, so that said elongated element is circumferentially distributed onto the toroidal support itself; transverse-distribution devices or other convenient transverse-distribution means arranged to give a relative movement between the toroidal support and said delivery member, for distributing said elongated element so as to form a plurality of coils disposed in side by side relationship in order to define a tire component.
Manufacturing of tires for vehicle wheels involves formation of a carcass structure essentially consisting of one or more carcass plies having a substantially toroidal configuration and the axially opposite side edges of which are connected to respective circumferentially-inextensible annular reinforcing elements, usually named xe2x80x9cbead coresxe2x80x9d.
Applied to the carcass structure, at a radially outer position thereof, is a belt structure comprising one or more belt strips in the form of a closed ring, essentially made up of textile or metallic cords suitably oriented in respect of each other and of the cords belonging to the adjacent carcass plies.
At a radially outer position relative to the belt structure, a tread band is then applied which usually consists of a strip of elastomer material of suitable thickness.
It is to point out that, to the purposes of the present description, by the term xe2x80x9celastomer materialxe2x80x9d it is intended the rubber blend in its entirety, that is the bled formed of at least one base polymer suitably amalgamated with reinforcing fillers and process additives of various types.
Ultimately, on the opposite sides of the tire being manufactured, a pair of sidewalls is applied, each of which covers one side portion of the tire included between a so-called shoulder region, located close to the corresponding side edge of the tread band, and a so-called bead located at the corresponding bead core.
Traditional production methods essentially provide that the above listed tire components should be first made separately of each other, to be then assembled in a tire-manufacturing step.
The Applicant""s present trend is however that of resorting to production methodologies enabling production and stocking of semi-finished products to be minimized or, possibly, eliminated.
Practically, the Applicant""s research and development are oriented towards new process solutions enable to manufacture the individual components applying them directly to the tire being manufactured according to a preestablished sequence.
On the other hand, from U.S. Pat. No. 5,453,140 it is known a method and an apparatus forming a carcass ply by laying down a plurality of parallel cords disposed circumferentially in side by side relationship onto a rigid toroidal support the shape of which matches that of the tire to be obtained, which cords are drawn from a continuous cord sequentially cut into lengths of appropriate size.
The Applicant too has developed manufacturing methods for forming a carcass structure, in which the carcass plies are obtained by laying down onto a rigid toroidal support, strip-like lengths obtained by sequentially cutting a continuous element made up of several cords incorporated into a layer of elastomer material.
Within the manufacturing scope of the carcass structure, as well as of other structural tire components such as sidewalls and tread band for example, manufacturing processes have been also proposed which aim at obtaining the desired component by laying down onto the tire being worked, a continuous strip-like element of elastomer material of a reduced section relative to that of the component to be obtained, and such arranged as to form a plurality of coils disposed consecutively in side by side and/or overlapped relationship around the rotation axis of the tire, so as to define the component itself in its final configuration.
In more detail, in U.S. Pat. Nos. 4,963,207 and 5,171,394 a method and an apparatus are respectively described in which given tire components are obtained by laying down a strip-like element of elastomer material onto a rigid toroidal support, which strip-like element is continuously fed from a delivery member associated with a volumetric extruder.
While the toroidal support is rotated around its own geometric axis, giving rise to a circumferential distribution of the strip-like element, the volumetric extruder is moved so as to impart controlled displacements to the delivery member in a meridian plane of the toroidal support, in order to distribute the different coils formed by the continuous strip-like element according to a predetermined pattern.
In U.S. Pat. No. 5,221,406 it is provided that a plurality of volumetric extruders should be arranged around the toroidal support, each of them being adapted to feed, through its own delivery member, a respective continuous strip-like element to be selectively employed for making a given tire component.
In accordance with the present invention, it has been found that if the controlled relative displacements between the toroidal support and delivery member are carried out by directly moving the toroidal support, instead of the extruder or any other apparatus associated with the delivery member itself, important advantages can be achieved in terms of simplification of the production plants, operation flexibility and productivity, as a result of a reduction in working dead times.
In more detail, it is an object of the present invention a method of manufacturing components for a tire for vehicle wheels, characterized in that said transverse-distribution displacements are performed by moving the toroidal support.
In more detail, both driving in rotation and movements of the toroidal support are preferably carried out by a robotized arm carrying the toroidal support itself.
Advantageously, the transverse-distribution displacements are carried out by moving the toroidal support according to at least five axes of oscillation, and more preferably according to at least six axes of oscillation.
It may be also advantageously provided that during the circumferential distribution of said at least one elongated element, the toroidal support should be moved keeping such an orientation that its geometric axis will be greatly inclined, preferably at an angle greater than 45xc2x0, relative to a horizontal plane.
It may be also provided that feeding of the elongated element should be carried out by extrusion through said delivery member, said elongated element being at least partly made of a raw elastomer material.
The toroidal support can be advantageously brought in front of said delivery member by said robotized arm, after removal of the toroidal support itself from a work station intended for executing a previous working step on the tire itself.
In accordance with the method in reference, the step of moving the toroidal support away from said delivery member by said robotized arm may be also provided, in order to transfer it either in front of at least another delivery member for formation of a further tire component or to a work station for carrying out a subsequent work step on the tire.
Said work station may be advantageously intended for formation of at least one carcass ply by sequential deposition of strip-like elements onto the toroidal support, the latter being supported and driven by the robotized arm, in a step-by-step movement around said geometric axis in synchronism with deposition of the individual strip-like elements, so as to give rise to a distribution of the strip-like elements according to a predetermined circumferential pitch.
It is also an object of the invention an apparatus for manufacturing components for a tire being worked, characterized in that said transverse-distribution devices or other convenient transverse-distribution means operate on said toroidal support for moving it with respect to the delivery member.
Advantageously, said circumferential-distribution means and said transverse-distribution means are integrated into a robotized arm.
More in particular, in a preferential embodiment the robotized arm comprises: a first section having a first end rotatably connected to a support platform according to first and second oscillation axes perpendicular to each other; a second section connected to a second end of the first section in an oscillating manner according to a third and a fourth oscillation axes perpendicular to each other; an end head arranged to engage rotatably and preferably in overhanging the toroidal support around the geometric rotation axis of the former, and connected to the second section in an oscillating manner at least according to a fifth axis of oscillation perpendicular to said fourth oscillation axis.
In more detail, said end head is in addition susceptible of oscillation around at least one sixth axis perpendicularly oriented with respect to the fifth oscillation axis.
At least one further work station is in addition preferably provided which is spaced apart from said feeder means and arranged to carry out a different work step on the tire, said robotized arm being arranged to transfer the toroidal support between said feeder means and work station.
Said further work station can be conveniently intended for making at least one carcass ply by sequential deposition of strip-like elements onto the toroidal support, said robotized arm being arranged to make the toroidal support rotate in a step-by-step movement around said geometric rotation axis, to cause a distribution of the strip-like elements according to a predetermined circumferential pitch.